Conventionally, strong acidic water is utilized as washing water for sterilization or disinfection in hand washing face washing, dish washing, washing of medical equipment, etc. (for example, see PTL 1). Strong acidic water can be obtained by electrolysis of an electrolytic solution, such as water, and it is generally produced by electrolysis of an aqueous chloride salt solution, which uses sodium chloride etc. as an electrolyte.